1. Field of the Invention
The invention relates to photographic materials processing apparatus and more particularly to a light tight processing tank apparatus for the processing or treating of photographic material such as the developing, fixing and washing of photographic film and paper, either black and white or color.
2. Description of the Prior Art
Equipment such as tank processors for photographic film and print material, in roll and sheet form, are well known in the art. Due to the necessity of assuring complete and rapid removal and changing of processing chemical solution to eliminate uneven development and contamination of one processing solution by another solution, processing tanks have been provided with means for filling through the top and draining through the bottom to avoid the necessity of having to invert the tank to drain processing solution. However, such prior art processing devices provided with bottom drain means are rather complex in construction and are often difficult or awkward to operate. In addition, the structure of such prior art processing tanks generally does not take into consideration the desirability and/or necessity for the recovery of processing solutions to minimize the expense incident to the processing of photographic films and papers. Some prior art processing tanks provided with a bottom drain valve do include a manual drain valve operator but the complexity and/or operation thereof is not suited to the rapid efficient draining of the processing solution and more significantly is not constructed so as to readily facilitate the recovery of processing solutions for reuse or servicing of the valve to remove potentially contaminating deposits of precipitated processing chemicals or solubilized light sensitive emulsion constituents. In this regard U.S. Pat. Nos. 1,208,244; 2,530,734; 2,748,678 and 3,677,163 are exemplary of prior art processing tanks of the above described general structure. Another shortcoming of prior art developing tanks is that they are generally not of variable capacity or of variable vertical extent and therefore are not suitable for providing a tank of exactly the proper size for the intended job so as to efficiently utilize processing solutions and minimize entrainment of air during agitation to minimize spotting from air bubbles that keep the processing solutions from uniformly acting upon the photographic emulsion.